Blood perfusion entails encouraging blood through the vessels of the body. For such purposes, blood perfusion systems typically entail the use of one or more pumps in an extracorporeal circuit that is interconnected with the vascular system of a patient. Cardiopulmonary bypass surgery typically requires a perfusion system that provides for the temporary cessation of the heart to create a still operating field by replacing the function of the heart and lungs. Such isolation allows for the surgical correction of vascular stenosis, valvular disorders, and congenital heart defects. In perfusion systems used for cardiopulmonary bypass surgery, an extracorporeal blood circuit is established that includes at least one pump and an oxygenation device to replace the functions of the heart and lungs.
More specifically, in cardiopulmonary bypass procedures oxygen-poor blood, i.e., venous blood, is gravity-drained or vacuum suctioned from a large vein entering the heart or other veins in the body (e.g., femoral) and is transferred through a venous line in the extracorporeal circuit. In some cases, blood is drained inside a reservoir that filters out solid and gaseous emboli, while in other cases such as in mini bypass applications, a relatively small volume venous bubble trap can be used instead of a large volume venous reservoir. The venous blood is pumped to an oxygenator that provides for oxygen transfer to the blood. Oxygen may be introduced into the blood by transfer across a membrane or, less frequently, by bubbling oxygen through the blood. Concurrently, carbon dioxide is removed across the membrane. The oxygenated blood is filtered and then returned through an arterial line to the aorta, femoral, or other artery.
Often, an arterial filter is added to the extracorporeal circuit, after the oxygenator, as a last barrier before the patient, so as to block any solid or gaseous emboli and prevent any such emboli from entering into the aorta of the patient. Recently, arterial filters integrated in the oxygenator have been developed, allowing the reduction of the priming volume of the circuit and decreasing the global haemodilution of the patient. In some cases, excessive haemodilution is one of the major post-operative causes of patient morbidity, and should be avoided.